The present disclosure relates to a toner transportation device that supplies toner to a developing unit, an image forming apparatus that includes the toner transportation device, and a method of detecting the amount of toner remaining.
In related art electrophotographic image forming apparatus, a developing process is performed by supplying toner from a developing unit to an electrostatic latent image formed on the surface of a photosensitive drum. The toner used in developing processes is supplied to the developing unit from the toner transportation device which includes, for example, a toner container and an intermediate hopper that contain toner.
As the developing process is repeated, the amount of toner remaining in the toner container decreases. The toner container needs to be replaced when the toner runs out. To determine when to replace the toner container, a typical image forming apparatus has a configuration for detecting or calculating the amount of toner remaining in the toner container. Examples of such a configuration include a design wherein a permeability sensor is provided to detect the change in permeability in the toner container associated with a reduction in the amount of toner, and a configuration in which an optical sensor is provided to detect the change in light transmittance in the toner container associated with a reduction in the amount of toner. There is also a design wherein the amount of toner consumption is calculated based on the number of dots in a developed image, and the amount of toner remaining in the toner container is estimated based on the calculated amount of toner consumption.
However, in the method that detects light transmittance in the toner container using an optical sensor, contamination of the toner container may cause an erroneous detection. The method that detects permeability in the toner container using a permeability sensor is not applicable to nonmagnetic toner. Moreover, in this method, variations in magnetic force may cause an erroneous detection. Estimating the amount of toner remaining in the toner container based on the number of dots in a developed image, indirectly estimates the amount of remaining toner using the number of dots. Because this tends to cause an error between the estimated amount of remaining toner and the actual amount of remaining toner, it is difficult to accurately estimate the amount of remaining toner.